The objective of the proposed work is to provide an understanding of the mechanisms of mitochondrial calcium transport, first in liver and later in other tissue. The areas of research effort and goals chosen to reach the objective are to identify and describe the separate mechanisms of mitochondrial calcium transport, to use this knowledge of the separate systems, where possible reconstituting them in a vesicular system, and finally to use the available knowledge of transport mechanisms to shed more light on the physiological significance of calcium transport. Current work in progress involves: (1) Studies of the kinetics of both influx and efflux mechanisms of liver mitochondrial calcium transport in both intact mitochondria and submitochondrial particles, (2) Studies of the sidedness and techniques of energizing submitochondrial particles, and (3) Studies of the properties of cytochrome oxidase vesicles reconstituted with certain selected mitochondrial hydrophobic protein fractions.